1 INTRODUCTION

THAT OXYGEN in our atmosphere can cause the deterioration of many organic materials found in museum objects has long been recognized1, and the general nature of these oxidative processes has been reviewed by Feller.2,3 The possibility of decreasing the rate of fading of organic colorants in museum objects by placing the objects in an oxygen-free environment has, from time to time, been suggested, and recent work by scientists in the conservation profession has made possible the construction of “microenvironmental” cases capable of maintaining an atmosphere of an inert gas with as low as 0.06% residual oxygen.4,5 Nevertheless, the use of such cases for the storage or display of museum objects has not been widespread. This is so in part because of the expense involved in the construction and maintenance of such cases and in part because of the absence of quantitative information to indicate the degree of enhancement in the life expectancy of colorants under an inert gas environment.

The objectives of this project were to determine (1) how effective an oxygen-free environment is in decreasing fading rates of organic colorants and (2) how much oxygen must be removed from a display case before a significant decrease in the rate of fading is achieved. The results indicate that the fading of many organic colorants is not halted entirely by removal of oxygen and that the degree of enhancement of life expectancy varies from colorant to colorant. On the other hand, the results also suggest that for most organic colorants at least 90% of the beneficial influence of a completely oxygen-free environment can be achieved in a display case containing as much as 0.2% residual oxygen.